cheatle



Nov. 26, 1957 w. R. CHEATLE CATHODE SPREADER FOR FLAT CATHODES OriginalFiled. July 10. 1953 INVENTOR WILFRED R. CH EATLE'.

United States Patent "ice 2,814,223 1 CATHODE SPREADER FOR FLAT CATHODESWilfred R. Cheatle, Emporium, PaL, assignor to Sylvania ElectricProducts, Inc., a corporation of Massachusetts Original application July10, 1953, Serial No. 367,261.

. Divided and this application November 13, 1956, Serial claims. ((31.8115) This inventionrelates to tools for use during the mannfacture ofanelectron tube and particularly for use with a hollow element withinthe tube which is to be reshaped by bowing of the sides thereof.

In particular, the invention relates to a tool for insertion within acathode sleeve which is placed within ,a wound grid in order to bringsurfaces of the sleeve very close to the wound grid.

In order to obtain certain characteristics in a tube, it is sometimesnecessary-to have the distance between electrodes very small. having ahigh mutual conductance or Gm, the distance between control grid andcathode should be made very small. In assembling such tubes whereadjacent electrodes are of the final desired dimensions, one electrodeis apt to rubagainst the other'with possible injury to the electrodes ortheir coatings.

It is an object of this invention to provide a tool for carrying out themethod so that there is much less likelihood of injury to the tubecomponents during assembly than heretofore, while yet providing for asimple method of finally forming the assembled parts to obtain desiredpositional relationships of the parts.

Fora better understanding of my invention, attention is directed to thefollowing specification and claims and the accompanying drawings inwhich:

Fig. 1 is a perspective view of a typical mount of a tube having a hightransconductance, parts being broken away to expose salient portions ofthe mount, and with the cathode bowing exaggerated to better illustratethe construction of the type of tube here involved.

Fig. 2 is a diagrammatic plan view of the triode portion of the mount.

Fig. 3 is a diagrammatic plan View of the cathode, grid and a fragmentof a support wafer prior to spreading of the cathode, the opening in thewafer for reception of the cathode being exaggerated as to minor axisdiameter.

Fig. 4 is a view similar to Fig. 3, but with the cathode spread, thefigure also showing, in section, the tool utilized in the process.

Fig. 5 is a view of one form of a tool employed in the process, showingthe proportion of parts.

Fig. 6 is a very much enlarged perspective view of one form of toolutilizable in the manufacture of the mount, the handle being brokenaway.

Fig. 7 is a section through the tool at its spreader portion, takenalong the line 77 of Fig. 6.

Fig. 8 is a view similar to Fig. 6 showing a modified form of tool.

Fig. 9 is a view showing a modified form of mounting the tool, only aportion of the tool being shown.

Referring to Fig. 1 there is shown a vacuum tube mount 10 with cathode12, grid 14 and anode 16. For exemplification, the tube disclosed is a6J4WA type which requires exceedingly close cathode and grid. Thecathode is suitably held between a pair of insulating wafers 24, and thegrid is supported by grid side rods 26, which may In the case of a gridcontrolled tube 6 slightly distend the large area faces of the cathode.

, 2,814,223 Patented Nov. 26, 1957 rectangle are bowed outwardly veryslightly. An exaggerated bow in the Wafer 24 is shown in Fig. 3 at 30.

In assembling themount, the bottom wafer has first assembled on it thecathode 12 in its parallepipedon form and the anode assembly 16. Thenthe grid structure 12 is slipped over the cathode and mounted on thelower wafer, and the top insulating wafer, provided with openingssimilar to the bottom wafer, is applied to the mount. The parts are thenfastened together. In the case of manufacture of diodes, the anodesmight be mounted very close to the cathode so that were an attempt madeto mount parts to occupy their final positions, damage to theelectrodes, particularly to the coating on the cathode, may well takeplace. Therefore, even in the assembly of a diode mount, it is desirableto follow the teaching of this inventor. Following such teaching, thecathode to be mounted should be of a cross section, notnecessarily'rectangular, such that it may be spread to bring parts of itcloser to the anode or anodes.

To complete the mount assembly, a cathode spreading tool, about to bedescribed, is inserted into the cathode along the axial center of thecathode and is rotated to In the process, because the distention isslight, no damage "is done to the cathode coating; the insulating wafer,if

provided with a rectangular opening, will yield the slight amountnecessary. Where the wafers hai e bowed wall openings, the distention ofthe cathode may be more freely accomplished without injury to thewafers. It has been found in practice, that by utilization of the toolfollowing the teachings of this invention, the losses in manufacture arefar below those where the assembly is effected without tools and withprebowed cathodes. In the prior art method damage to the cathode coatingor distortion of other electrodes is a quite frequent occurrenceresulting in considerable tube losses or shrinkage.

The tool 32 comprises a socketed handle 34 and a needle 36 secured inthe handle by any convenient means such as a set screw 38 threaded intothe handle and engaging the needle portion lying in the socket of thehandle. The needle 36 itself is comprised of a cylindrical portion 40and a second spreader portion 42 of reduced diameter with respect to thecylindrical portion to provide a shoulder 44 for a purpose to bedescribed. The free end of the needle may be tapered as shown at 45.

The spreader has two parallel fiat sides 46 spaced apart a distancebarely under the minor diameter of the unspread cathode and two opposedrounded surfaces 48 whose maximum spacing is equal to the desire-d finaldistended internal minor dimension of the cathode. The handle 34 has aflat portion 50 parallel to the fiat face 46 of the spreader toindicate, to the operator by feel, the angular position of the spreaderflat faces. Instead of the needle being mounted in a socketed handle, itmay obviously project upwardly from a flat base 60, as is shown in Fig.9, resting on a suitable support such as a table.

In use, after the parts of the tube have been mounted as describedabove, the spreader is inserted into the cathode at about its mediallongitudinal axis and thrust in until the shoulder 44 engages the edgeof the cathode.

Then the tool and the cathode are relatively rotated 180 or more, thuscausing the rounded edges of the needle to engage the cathode walls tobe bowed. Since the maximum distance between the rounded ends of thetool is greater than the distance between the walls to be bowed, thereWill be effected a spreading of the cathode to bring the outer face ofthe cathode closer to the grid. After the cathode has been spread, thetool is retracted. The mount then is further processed, as is usual inthe art.

If desired, particularly where wafers with rectangular openings for thecathode are provided and in order to prevent possibility of breakage ofthe wafer when the cathode is enlarged, the form of spreading tool shownin Fig. 8 may be employed.

This tool differs from the tool previously described in that not onlythe free end 52 of the spreader, but also the end 54 adjacent to theshoulder 56 have their rounded cylindrical sides approach each othervery slightly. Thereby neck portions are formed at both ends of theneedle. As a result, when the tool is inserted in a rectangular cathodeand rotated, the cathode will spread between the wafers; at the level ofthe wafers, the spread will be exceedingly little, if at all, thusreducing any tendency for the wafer to crack or crumble. Where thewafers are provided with rectangular holes, the cathode is slightlybulged between the wafers and held against excessive longitudinalmovement with respect to the wafers when the parts are cold. The lengthof the operative surfaces of the needle is proportioned to the length ofcathode between wafers to secure this result.

This application is a division of application Serial No. 367,261, filedJuly 10, 1953.

Having thus described the invention, what is claimed as new is:

1. A spreading tool comprising a generally cylindrical handle and aneedle member supported by the handle. the needle member comprising aportion whose boundary is generally elliptical with parallel flat wallsand cylindrical connecting walls between the edges of the fiat walls,there being a fiat surface on the handle member parallel to a fiat wallon the needle portion to facilitate positioning the tool.

2. A spreading tool comprising a handle and a needle member supported bythe handle, the needle member comprising a cylindrical portion adjacentthe handle and an elongated following portion, ellipsoidal in crosssection, the length of the major axis of the ellipsoid throughout itslength and at its juncture with the cylindrical portion being less thanthe diameter of the cylindrical portion to form a collar on the end ofthe cylindrical portion and whose minor axis terminates in a pair ofparallel sides.

3. A tool for spreading cathodes comprising a mounting and a needleportion carried thereby, said needle portion including an elongated partgenerally cylindrical but having two parallel plane surfaces, therounded surfaces at spaced points along the elongated part approachingthe axis of the cylinder to form neck portions.

4. A tool for spreading cathodes comprising a mounting and a needleportion carried thereby, said needle por- {tion comprising a cylindricalportion attached to the handle and a second portion in axial alinementwith the cylindrical portion and forming a prolongation thereof, saidsecond portion being generally cylindrical but with parallel planewalls, the cylindrical wall portions adjacent the ends of the secondportion approaching the axis of the cylinder to form reduced neckportions, there being a shoulder at the juncture of the two portions ofthe needle.

5. A tool for spreading cathodes comprising a mounting and a needleportion carried thereby, said needle portion including an elongated partgenerally cylindrical but having two parallel plane surfaces, an end ofthe part having its rounded surfaces approach the axis of the cylinderto form a portion of a smaller cross-sectional diameter.

References Cited in the file of this patent UNITED STATES PATENTS437,177 Deaton Sept. 30, 1890 1,376,811 Hood May 3, 1921 1,677,572Walkley July 17, 1928 FOREIGN PATENTS 18,702 Great Britain of 1913

